const sun  = function(a,b){
	return parseInt(a)+parseInt(b)
}
const subtract = function(a,b){
     return parseInt(a) - parseInt(b)
}
const multiply = function(a,b){
    return parseInt(a) * parseInt(b)
}
const divide = function(a,b){
    return parseInt(a) / parseInt(b)
}
// 导出成员：
module.exports = {
	sun:sun,
	 subtract: subtract, 
    multiply: multiply, 
    divide: divide
}
/* //简写
module.exports = {
    sum, 
    subtract, 
    multiply, 
    divide
} */